1. Field of the Invention
The present invention relates generally to the field of controlling the flow of a gaseous fluid in a duct or system of ducts and, more particularly, to a damper or mixing system utilizing dampers which have substantially linear characteristics over the modulated range from fully closed to fully opened. The dampers, when properly combined, have the ability to produce excellent mixing of streams being combined beyond the dampers.
2. Description of the Prior Art
A great deal of effort has been put forth in an attempt to produce linear control action with dampers such that the fluid flowing in a duct is proportional to the angular opening of the damper. The general approach has been to select either opposed or parallel bladed dampers according to the particular application involved and, in some cases, to further attempt to linearize its operating characteristics by reducing the size of the damper in relation to the size of the duct involved. This, of course, increases total flow resistance and decreases the efficiency of the duct system.
Other prior art dampers and linkage include one shown in a U.S. Pat. No. to Hinden, 3,044,387, issued July 17, 1962, which illustrates and describes a linkage system in which damper blades may be operated in pairs. Such a system, however, does not achieve the results contemplated by the present invention.